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Artist's image of a firestorm of star birth deep inside the core of a young, growing elliptical galaxy NGC 4676 (Mice Galaxies) is an example of a present merger. The Antennae Galaxies are a pair of colliding galaxies – the bright, blue knots are young stars that have recently ignited as a result of the merger.
[f] Six planets, seven dwarf planets, and other bodies have orbiting natural satellites, which are commonly called 'moons'. The Solar System is constantly flooded by the Sun's charged particles, the solar wind, forming the heliosphere. Around 75–90 astronomical units from the Sun, [g] the solar wind is halted, resulting in the heliopause.
The currently accepted method by which the planets formed is accretion, in which the planets began as dust grains in orbit around the central protostar. Through direct contact and self-organization , these grains formed into clumps up to 200 m (660 ft) in diameter, which in turn collided to form larger bodies ( planetesimals ) of ~10 km (6.2 mi ...
2005 – Spitzer Space Telescope data confirm what had been considered likely since the early 1990s from radio telescope data, i.e., that the Milky Way Galaxy is a barred spiral galaxy. [14] [15] 2012 – Astronomers report the discovery of the most distant dwarf galaxy yet found, approximately 10 billion light-years away. [16]
The timeline of discovery of Solar System planets and their natural satellites charts the progress of the discovery of new bodies over history. Each object is listed in chronological order of its discovery (multiple dates occur when the moments of imaging, observation, and publication differ), identified through its various designations (including temporary and permanent schemes), and the ...
The Milky Way [c] is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galaxy, which are so far away that they cannot be individually distinguished by the naked eye.
A galaxy will continue to absorb infalling material from high-velocity clouds and dwarf galaxies throughout its life. [197] This matter is mostly hydrogen and helium. The cycle of stellar birth and death slowly increases the abundance of heavy elements, eventually allowing the formation of planets. [198]
The inner Solar System and the terrestrial planets. 2021 PH27; Mercury. Mercury-crossing minor planets; Venus. Venus-crossing minor planets. 524522 Zoozve, Venus' quasi-satellite; Earth. Moon; Near-Earth asteroids (including 99942 Apophis) Earth trojan (2010 TK 7) Earth-crosser asteroids. Earth's quasi-satellites; 433 Eros; Mars. Deimos; Phobos ...